32 JUNE 2015 • WORLD AQUACULTURE • WWW.WAS.ORG Atlantic Salmon In the fall of 1975 AKVAFORSK started a familybased breeding program (the Norwegian model), with the first generations selected for increased growth rate. The base population consisted of crosses between 41 river strains of Atlantic salmon. The first generation of selection resulted in a 15 percent genetic gain. In the fifth generation the selected stock was compared with wild salmon and feed consumption was recorded as one of the traits investigated. The results demonstrated a 113 percent gain in growth rate (averaging 13 percent per generation) and the selected fish had better retention of protein (9 percent) and energy (14 percent) and 23 percent improvement in feed conversion ratio (FCR). This breeding program has been continued by the commercial breeding company Aqua Gen AS (www.aquagen.no) and, to the present time, has been through 11 generations of selection. I estimate that the accumulated improvement in FCR in this stock currently exceeds 30 percent compared to the base populations. The Norwegian salmon industry now produces more than 1.3 million tons per annum and, through use of genetically improved stock, saves in the range of 120,000 tons of feed annually (amounting to ~ US$ 700-800 million in reduced annual feed costs at current prices). Furthermore, the production output of a standard farm has doubled, resulting in additional savings in labor cost and reduced mortality due to the shorter production cycle with improved genetic material. Farmed Atlantic salmon now typically reach the harvest size of 4 kg in less than two years, as compared to four years in the 1970s. Nile Tilapia In 1988, the International Center for Living Aquatic Resources Management (presently The World Fish Center) invited AKVAFORSK to start a breeding program with Nile tilapia in the Philippines to demonstrate that the Norwegian model used for genetic improvement of Atlantic salmon and rainbow trout could also be successfully applied to a tropical fish species. The project and the fish were called GIFT, for Genetically Improved Farmed Tilapia. The base population for selection was recruited from crosses among eight strains: four wild strains collected from Africa and four strains available in the Philippines. The family-based breeding program selected for only growth rate during the first five The Clear Need for Breeding Programs in Aquaculture Trygve Gjedrem generations (over five years). The accumulated genetic gain was 85 percent (on average 13 percent per generation). GIFT fish were subsequently spread to many countries and major breeding programs originating from the original GIFT program have continued in countries like Malaysia, Vietnam, China and the USA. Global production of Nile tilapia was more than 3.1 million tons in 2012, increasing at 12 percent per year. GIFT fish account for the majority of global tilapia production today. If the present trend continues, Nile tilapia will be the fish species with greatest production in 2018. Disease Resistance Several selection experiments have demonstrated genetic gains of around 14 percent for several diseases. Stable results are achieved by challenge testing individual families with specific disease causing organisms. In addition, positive genetic correlations have been recorded between growth rate and survival in most fish species. Genetic markers (QTL) explain more than 80 percent of the genetic variation in resistance to infectious pancreatic necrosis in Atlantic salmon. Likewise, a combined array of genetic markers explain a significant proportion of other diseases such as pancreas disease in the same species. These results mean that it is possible to develop more diseaseresistant strains for several diseases. How fast gains are made will depend on the relative weights allocated to disease traits as compared to other traits in establishing breeding goals. These examples and a number of other reports, both in fish and shellfish, clearly demonstrate the power of family-based selection schemes as means to improve productivity in farmed aquaculture species. Disappointments In 2010, two review papers estimated that only 10 percent of aquaculture production at that time was based on genetic material improved through selective breeding. Hopefully this proportion is greater in 2015. Being aware of the untapped potential for improvements through selection, it is greatly disappointing that we still lack well-designed breeding programs for so many farmed aquaculture species. This means that the majority of aquaculture production is based on wild stocks and stocks where individuals at best are selected for growth rate but without consideration of The Norwegian salmon industry now produces more than 1.3 million tons per annum and, through use of genetically improved stock, saves in the range of 120,000 tons of feed annually (amounting to ~ US$ 700-800 million in reduced annual feed costs at current prices). Furthermore, the production output of a standard farm has doubled, resulting in additional savings in labor cost and reduced mortality due to the shorter production cycle with improved genetic material. Farmed Atlantic salmon now typically reach the harvest size of 4 kg in less than two years, as compared to four years in the 1970s.
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